The present invention relates to a sheet supply apparatus mounted to an image forming apparatus (called an image forming apparatus below), such as a copier, printer apparatus or a facsimile machine, and more particularly, it relates to an automatic supply apparatus which is detachably mounted to an image forming apparatus equipped with aligning means that supplies sheets to an image forming means while aligning an edge of supplied sheets to a transport reference member.
Image forming apparatuses are equipped with a supply portion to supply stacked sheets and with image forming means to form images or characters on sheets supplied from the supply portion, and the sheets are transported from the sheet supply portion to the image forming means in a sheet transport path disposed in the image forming apparatus.
In these kinds of image forming apparatus, in order to improve the image forming quality by forming images on predetermined positions on the sheets, an image forming apparatus equipped with aligning means to supply sheets to the image forming means while aligning an edge of the sheets supplied from the sheet supply portion to accurately position the sheets has been provided for practical use. Examples of the image forming apparatuses equipped with such aligning means are disclosed in Japanese Patent Publication No. 08-208078 and U.S. Pat. No. 05,494,277.
The apparatus disclosed is composed of an internal cassette tray for storing sheets inside the image forming apparatus, and the sheets stacked in these cassette trays are supplied to the image forming portion. Normally, the number of sheets stored in these cassette trays is approximately from 250 to 500, so when forming images on a large number of the sheets at a high speed, it is necessary to frequently replenish sheets. For that reason, an automatic sheet supply apparatus that can store a large number of the sheets has been required.
Such a large capacity automatic sheet supply apparatus, as disclosed in Japanese Patent No. 02,625,057 or U.S. Pat. No. 05,368,285, are equipped with an ascending and descending paper deck (support stage) that supports a large number of stacked sheets (generally, approximately from 2,000 to 3,000 sheets) and separation supply means to separate sheets stacked on this paper deck into single sheets and to supply them to a resister roller on the image forming apparatus.
Also, as an apparatus embedded in the image forming apparatus, Japanese Patent Publication (Tokkai) No. 11-30884 disclosed an example of reducing a transport load when transporting on the rollers arranged on the downstream side in the transport path by separating the upstream paired relay rollers after the sheet has reached the downstream side transport rollers. The separation of the paired relay rollers is performed by mounting one roller to a swinging lever and moving this lever using a solenoid.
However, there are several problems associated with mounting the aforementioned aligning means equipped with the conventional large capacity automatic sheet supply apparatus to an image forming apparatus.
Firstly, after the sheets from the automatic sheet supply apparatuses reach the aligning means on the image forming apparatus, they are moved in a direction traversing the sheet transport direction along the transport reference, but when the sheets are nipped in the separation supply means, the sheets are not smoothly moved in the sheet transport reference side. Particularly, increasing the transport force of the alignment means increases the possibility for the sheets to overrun the transport reference, or when using thin sheets, to bent their edges, and with the pressing contact of the separation supply means, alignment is substantially impossible.
Secondly, it is conceivable to arrange the sheet transport reference on the image forming apparatus side or the alignment means on the sheet automatic sheet supply apparatus, but in this case, it would be unavoidable to increase the size of the sheet supply apparatus.
Thirdly, the aforementioned sheet supply apparatus becomes larger to dispose aligning means in the image forming apparatus to perform resister correction for aligning the leading edge of the sheets supplied after separating and supplying the sheets. For that reason, if the resister means is eliminated, only the aligning means corrects the sheets, thereby making it difficult to perform the proper aligning correction when processing sheets with large bends.
The first object of the present invention is to provide a sheet supply apparatus that can use aligning means to securely align a sheet at a reference position even if the sheet supply apparatus is mounted to an image forming apparatus equipped with the aligning means.
The second object of the present invention is to provide an apparatus that can mount a sheet supply apparatus to an image forming apparatus equipped with aligning means, and also to provide a compact apparatus that performs resister correction with the sheet supply apparatus in advance.
The third object of the present invention is to provide an apparatus that can mount a sheet supply apparatus to an image forming apparatus equipped with aligning means, and also to provide a sheet supply apparatus that can separate and supply sheets at a high speed even if the sheets has various thickness.
Furthermore, an object of the present invention is to provide a sheet supply apparatus that can supply sheets efficiently at a high speed through properly supplying or transporting the sheets according to control of a sheet nipping state or a sheet releasing state at a sheet separating means and a resister roller means when the sheets are supplied from the sheet separating means to the resister roller means in the sheet supply apparatus or when the resister roller means performs resister correction and the sheets are supplied downstream.
In order to attain the aforementioned objectives, the present invention is a sheet supply apparatus that supplies sheets to an image forming apparatus unit having sheet aligning means for aligning the sheets to a predetermined sheet transport reference in a sheet transport direction. The sheet supply apparatus includes sheet storage means for stacking and storing the sheets; sheet pick-up means for feeding the sheets from the aforementioned sheet storage means; separating means having supply rollers for supplying the sheets fed from the aforementioned sheet pick-up means and separating members pressing the aforementioned supply rollers; a pair of resister rollers for feeding the sheets to the aforementioned aligning means after resister correction for aligning a transport direction of the sheets separated and transported in the aforementioned separating means; and a frame for supporting each of the aforementioned means. The sheet supply apparatus is also provided with the first press separating means for the aforementioned supply rollers and the aforementioned separating members to be in a sheet nipping state or a sheet released state, and the second press separating means for the aforementioned pair of the resister rollers to be in a sheet nipping state or a sheet released state.
In the sheet supply apparatus according to the present invention, it is possible for the aligning means to securely align the sheets at a reference position because the sheet nipping state is released after the sheets are fed to the aligning means in the image forming apparatus.
Further, the present invention is an image forming apparatus that comprises the first unit having sheet aligning rollers for aligning sheets at a predetermined sheet transport reference side in the sheet transport direction while transporting the sheets, and the second unit detachably mounted to the aforementioned first unit. The second unit includes sheet storage means for stacking and storing the sheets; sheet pick-up means for feeding the sheets from the aforementioned sheet storage means; separating means having supply rollers for supplying the sheets fed from the aforementioned sheet pick-up means and separating members pressing the aforementioned supply rollers; a pair of resister rollers for feeding the sheets to the aforementioned aligning means after resister correction for aligning a transport direction of the sheets separated and transported in the aforementioned separating means; and a frame for supporting each of the aforementioned means. The image forming apparatus is also equipped with the first press separating means for the aforementioned supply rollers and the aforementioned separating members to be in a sheet nipping state or a sheet released state, and the second press separating means for the aforementioned pair of the resister rollers to be in a sheet nipping state or a sheet released state.
With this configuration, after the sheets are fed to the unit comprising the sheet aligning rollers, the sheet nipping is released, thereby enabling the secure positioning alignment of the sheets using the aligning means.
Still further, the present invention is a sheet supply apparatus equipped with separating means comprising supply rollers and separating members pressing the rollers disposed in a sheet transport path; a pair of relay rollers for transporting sheets separated by the separating means in a transport direction downstream of the sheet supply path; the first drive means for rotating the aforementioned supply rollers in a sheet supply direction with forward rotation, and having the first press separating means for the aforementioned supply rollers and separating members to be in a sheet nipping state or a sheet released state with reverse rotation; the second drive means for rotating the pair of the relay rollers in a sheet supply direction with forward rotation, and having the second press separating means for the pair of the relay rollers to be in a sheet nipping state or a sheet released state with reverse rotation; and a drive control means for the supply rollers and the separating means to be in the sheet released state by switching the aforementioned first drive means from the forward rotation to the reverse rotation after a leading edge of the sheets reaches the pair of the relay rollers, and for the pair of the relay rollers to be in the sheet released state by switching the second drive means from the forward rotation to the reverse rotation after the leading edge of the sheets reaches the predetermined position downstream in the sheet transport direction.
Therefore, according to the present invention, when sequentially feeding the sheets between the rollers, it is possible to drive for feeding the sheets with the rollers and to move the rollers to the sheet nipping released state with one single motor. Thus, it is possible to smoothly feed the sheets to the aligning means for aligning the sheets at the predetermined sheet transport reference in the sheet transport direction from the sheet supply apparatus with a simple mechanism.
In addition, the present invention is a sheet supply apparatus for separating and supplying stacked sheets includes sheet storage means for stacking and storing the sheets; sheet pick-up means for feeding the sheets from the aforementioned sheet storage means; separating means having supply rollers for supplying the sheets fed from the sheet pick-up means and separating members pressing the supply rollers; a pair of resister rollers for aligning a leading edge of the sheets separated by the aforementioned separating means and for feeding the sheets to transport rollers arranged downstream in a sheet supply path; the first press separating means for the aforementioned separating means to be in a sheet nipping state or a sheet released state; the first drive means for driving the aforementioned separating means; the second press separating means for the pair of the resister rollers to be in the sheet nipping state or the sheet released state; and the second drive means for driving the pair of the resister rollers. The first press separating means shifts the aforementioned separating means from the sheet nipping state to the sheet released state after the sheets are fed to the pair of the resister rollers, and shifts the aforementioned separating means to the sheet nipping state after the sheet trailing edge passes the separating means.
With this configuration, it is possible to supply the sheets to the image forming apparatus at a high speed because the sheet pick-up means feeds the next sheet to the sheet separating means while the separating means switches from the sheet released state to the sheet nipping state. Other objectives and features of the present invention will be clearly explained in the following detailed description with reference to the accompanying drawings.